1. Field of the Invention
The invention relates to a hydraulic pumping unit for feeding the hydraulic tilting cylinder(s) of a vehicle having a tilting cab, in which a control valve body is provided, at an end projecting beyond the pumping unit housing, with a handle by means of which the control valve body may be turned between at least two positions operative to tilt the cab from the drive position and to tilt the cab back into the drive position of the vehicle respectively.
2. Discussion of the Prior Art
Such a pumping unit, which is designed for manual control, is disclosed in EP-A-0212008. In this well-known pumping unit, the handle is formed by a pin that is extending radially through the projecting control valve end and enables the application of a moment that is large enough to overcome the friction between the control valve body and the bore.
For such pumping units, it is of importance that they can be protected against unauthorized control to prevent, in particular, the cab from being tilted from the driving position by unauthorized persons.
Various solutions have been proposed for this purpose. It has been known, e.g., to apply a solenoid valve in a supply conduit to the hydraulic tilting cylinder, which valve is normally closed and can be opened only by energization (e.g., through a key) from the cab in order to be able to have the tilting cylinder operate by means of the pumping unit.
It is also known to apply a normally opened solenoid valve in a connecting conduit between the pressure conduit and the return conduit of a hydraulic tilting cylinder. In that case, for tilting the cab from the driving position, the valve has to be closed; this, however, can be effected only through electrical energization from the cab.
Such solutions require electrical wiring between the pumping unit and (the dash-board in) the cab, which involves an additional source of failures.
It is also known to prevent unauthorized persons from carrying out the pumping action by blocking the pumping lever or the control valve by means of a (pad) lock or by applying a lock which prevents the pump lever from being inserted in its connecting hub.
The use of separate locks, however, is awkward, whereas such additional means may easily get lost.